Abstract

We use statistical models for mean and extreme values of total column\nozone to analyze ``fingerprints{''} of atmospheric dynamics and\nchemistry on long-term ozone changes at northern and southern\nmid-latitudes on grid cell basis. At each grid cell, the r-largest order\nstatistics method is used for the analysis of extreme events in low and\nhigh total ozone (termed ELOs and EHOs, respectively), and an\nautoregressive moving average (ARMA) model is used for the corresponding\nmean value analysis. In order to describe the dynamical and chemical\nstate of the atmosphere, the statistical models include important\natmospheric covariates: the solar cycle, the Quasi-Biennial Oscillation\n(QBO), ozone depleting substances (ODS) in terms of equivalent effective\nstratospheric chlorine (EESC), the North Atlantic Oscillation (NAO), the\nAntarctic Oscillation (AAO), the El Nino/Southern Oscillation (ENSO),\nand aerosol load after the volcanic eruptions of El Chichon and Mt.\nPinatubo. The influence of the individual covariates on mean and extreme\nlevels in total column ozone is derived on a grid cell basis. The\nresults show that ``fingerprints{''}, i.e., significant influence, of\ndynamical and chemical features are captured in both the ``bulk{''} and\nthe tails of the statistical distribution of ozone, respectively\ndescribed by mean values and EHOs/ELOs. While results for the solar\ncycle, QBO, and EESC are in good agreement with findings of earlier\nstudies, unprecedented spatial fingerprints are retrieved for the\ndynamical covariates. Column ozone is enhanced over Labrador/Greenland,\nthe North Atlantic sector and over the Norwegian Sea, but is reduced\nover Europe, Russia and the Eastern United States during the positive\nNAO phase, and vice-versa during the negative phase. The NAO's southern\ncounterpart, the AAO, strongly influences column ozone at lower southern\nmid-latitudes, including the southern parts of South America and the\nAntarctic Peninsula, and the central southern mid-latitudes. Results for\nboth NAO and AAO confirm the importance of atmospheric dynamics for\nozone variability and changes from local/regional to global scales.